The herein disclosed invention finds applicability in the field of chlorinated hydrocarbons preparation.
The inventor is developing a manufacturing process to produce isopropyl chloride (IPC, or 2-chloropropane) via the addition of anhydrous HCl to propylene. It is known in the art that the hydrochlorination process can be carried out in either the gas or liquid phases.
Nappa et al (U.S. Pat. No. 5,672,788) teach a process for preparing difluoroethane by reacting HCl with chloroethylene to produce dichloroethane and converting this product to difluoroethane. The Nappa et al process is distinct from the herein disclosed invention in that the reaction conditions are distinct, the starting materials are different as are the reaction conditions.
Arnold and Lessig (U.S. Pat. No. 2,097,750) teach the preparation of alkyl chlorides in the vapor phase by passing HCl and an alkene over a halide of a Group IIB metal supported on activated carbon. Example five in their patent describes the formation of isopropyl chloride by passing HCl and propylene over a catalyst of zinc chloride on charcoal at atmospheric pressure and 150 degrees C.
Holmes (U.S. Pat. No. 2,429,758) teaches anhydrous calcium sulfate (xe2x80x9cDrieritexe2x80x9d) to effect the reaction between HCl and propylene in the vapor phase. Temperatures and pressures ranged from 35 to 200 degrees C., zero to 100 psig.
Stabo and Trabalka, Romanian Patent RO 97443 (Jul. 31, 1989) describe the hydrochlorination of propylene, presumably in the liquid phase, between 0-120 degrees C. and 1-5 kgf/cm2 (0.3 to 1.7 psig) using aluminum chloride catalyst complexed with 1,1,1-trichloroethane, 1,1,2-trichloroethane, or 2-chloropropane.
Nakamoto et al, JP 60178831 (Sep. 12, 1985) reported a reaction using liquid isopropyl chloride as a solvent in the presence of a Friedel-Crafts catalyst, preferably ferric chloride. Preferred temperatures were  less than 30 degrees C. with an HCl/propylene molar ratio of  greater than 1.05. Cited ferric chloride concentration was 1 gram per 100 ml solution.
None of the prior art patents teach the inventive process of the herein disclosed invention.
An in-house development of a liquid-phase process for the production of isopropyl chloride began in late 1998. Very quickly, the preferred method became hydrochlorination of propylene in liquid isopropyl chloride solvent using ferric chloride catalyst and high HCl/propylene feed ratios (1.5/1 to 2/1 molar). The excess HCl served as a stripping gas to remove the IPC product from the reactor as a vapor. Reaction pressures and temperatures were kept low, e.g., below 15 psig and 40 degrees C., to minimize side reactions between propylene and the catalyst. These side reactions were believed to increase catalyst consumption and cause the formation of 1,2-dichloropropane and heavier components. Minimum concentration of the ferric chloride catalyst necessary to initiate and sustain the reaction ranged from 1000-6000 ppm by weight, depending upon the purity of the IPC initially charged to the reactor. These temperature and pressure ranges were based upon the Nakamoto et al above cited and the inventors"" own experience with its commercial operation to produce 1,1,1-trichloroethane by hydrochlorination of vinylidene chloride. The ferric chloride concentration was the minimum necessary to achieve a sustainable reaction.
A main object of this invention is for the efficient preparation of isopropyl chloride under conditions which preserve the catalyst.
A significant object of this invention is to produce isopropyl chloride under conditions which reduce by-product formation.
These and other objects of the present invention will become apparent from a reading of the following specification taken in conjunction with the enclosed examples.
In simplest terms the reaction of this invention is carried out by incorporating a ferric chloride catalyst (FeCl3) in IPC(2-chloropropane) as the solvent and sparging a proper ratio of HCl and propylene (in their gaseous form) through the IPC solvent containing FeCl3 catalyst. The HCl and propylene react to form IPC (isopropyl chloride). Some of the IPC is removed in vapor form from the reaction mixture by sparging with HCl. Most of the IPC is removed in the liquid phase. The preferred process is run on a continuous basis.
A process for the production of isopropyl chloride (IPC) via the ferric chloride-catalyzed liquid-phase hydrochlorination of propylene is described herein in detail. The improvement consists of operating the reactor at higher temperatures and pressures than those described in prior art preferred embodiments. This allows the concentration of ferric chloride catalyst to be reduced by at least a factor of ten, which improves catalyst life, lowers by-product formation, and reduces the amount of waste for disposal.
The method of this invention is designed to reduce the amount of ferric chloride necessary to catalyze the production of isopropyl chloride via liquid-phase hydrochlorination of propylene in isopropyl chloride solvent. The inventive process consists of operating the reaction at a higher temperature and pressure, which surprisingly reduces the concentration of catalyst needed, extends catalyst-life, and greatly reduces the formation of by-products via reaction of the catalyst with the solvent. The process also allows for the use of HCl/propylene molar feed ratios of approximately 1.0-1.2 without any significant loss in feed conversions. This reduces the amount of unreacted gas that must be recycled, thereby reducing the size of, or eliminating, a recycle compressor and associated equipment.
The process of the invention is for the production of isopropyl chloride via the liquid-phase hydrochlorination of propylene in isopropyl chloride solvent. The improvement consists in operating the reactor at a temperature of at least 50 degrees C. or higher and at a pressure of 30 psig or higher. Molar HCl to propylene feed ratio of 1.0 to 1.2 is used. Under these conditions, rapid reaction rates and greater than 90 percent feed conversions can be achieved using ferric chloride catalyst concentrations in the liquid solvent of 15-250 ppm by weight. These low catalyst concentrations greatly reduce side reactions between the ferric chloride and the solvent or feed materials. At higher catalyst concentrations, these side reactions cause the reactor solution to darken and develop a precipitate. At the claimed lower catalyst concentrations little or no solution darkening or solids formation occurs. Product isopropyl chloride can be removed from the reactor as a vapor, a liquid, or a combination of the two.
This contrasts with the prior art process which operated at 30 degrees C. or lower and at a total system pressure of 20 psig or less. Molar HCl to propylene feed ratios of 1.5 to 2.0 were used. To maintain rapid reaction rates and greater than 90 percent propylene conversion, ferric chloride catalyst concentrations in the liquid of 1000-6000 ppm by weight were required. The desired isopropyl chloride product was removed solely as a vapor using the unreacted HCl as a stripping gas.